People on average spend about 90% of their time indoors. The quality of air in office, residential, school, and industrial buildings can significantly affect the health and productivity of building occupants. Sick buildings, toxic molds, epidemics of asthma allergies, have made indoor air quality critical, in which Volatile organic compounds (VOCs) are among the most abundant chemical pollutants in the indoor air according to WHO [1] and USEPA [2]. The problems include eye; nose; and throat irritation, headache, recurrent fatigue, drowsiness, dizziness, and reduced power of concentration [3].
Therefore, for commercial residential and industrial buildings, providing a good ventilation system with air-purification device is a key to provide better indoor air quality (IAQ) and to save energy. Many advanced technologies related to air purification devices for removal of pollutants from indoor air have recently been developed. These air purification devices includes removal of particulate and gaseous that may be installed in the ductwork of building central heating, ventilating, and air-conditioning (HVAC) system to clean the air, or a kind of portable room air cleaners that can be used to clean the air in a single room or in specific areas.
There are two types of air-cleaning approaches commonly being used, one are mechanical air filters, such as high efficiency particulate air (HEPA) filters that remove particles by capturing them on filter materials, or electronic air cleaners such as electrostatic precipitators that use a process called electrostatic attraction to trap particles. Another type of air-cleaning device is air purification such as gas-phase adsorption filter designed to remove gases and odors by either physical or chemical processes. Specifically, the technology of gaseous removal air purifications include an activated carbon adsorption filter (ACA), photo-catalytic oxidation (PCO) devices, ultraviolet photocatalytic oxidization (UV-PCO), plasma ionization approach (PIA), ozone ionization approach (OIA), soil filtration technology (SFT), etc. The effectiveness of applying these techniques varies widely, some air cleaners are largely ineffective, and some produce harmful by-products.
A state-of-the-art review of all kinds of air purification technologies has been taken through over 160 scientific literatures [4]. The conclusions indicated that (1) none of the current technologies was able to effectively remove all indoor pollutants and many were found to generate undesirable by-products during operation, (2) Particle filtration and sorption of gaseous pollutants were among the most effective air cleaning technologies, but there is insufficient information regarding long-term performance and proper maintenance.
Accordingly a need exists in the art for improved techniques for air purification technologies and evaluation.